The nutritive value of faba bean silage for lactating dairy cows

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The nutritive value of faba bean silage for lactating dairy cows

Louw, Antony William

2009-03

ENGLISH ABSTRACT: The dry matter (DM) production and chemical composition of whole crop faba beans (Vicia faba) and oats
(Avena sativa) were determined according to fresh material harvested at weekly intervals. From 75 to 166 days
after planting whole plants of faba beans and oats were harvested at a height of ca. 10 cm above the ground on
five randomly selected areas of 0.25 m² each. The freshly harvested material was weighed “as is” and ovendried
to determine the DM content of each sample. The fresh and DM forage production per hectare was then
calculated. The crude protein (CP), crude fiber (CF), neutral detergent fiber (NDF), acid detergent fiber (ADF),
nitrogen free extract (NFE), fat (EE), calcium (Ca) and phosphorus (P) contents were determined according to
standard laboratory techniques. The change in chemical composition of fresh whole crop material was
regressed on days after planting using simple linear regressions. The fresh and DM production of whole crop
faba beans and oats increased with advancing growth stage. During the 2002 production year fresh yield
production of both whole crop faba beans and oats peaked at 131 days (44.7±6.9 and 28.4±7.1 ton/ha
respectively). DM yield peaked at 159 and 152 days for whole crop faba beans and oats being 9.4±1.3 and
8.8±0.7 tons DM/ha respectively. The chemical composition of both forage crops decreased with advancing
growth stage. The CP content of whole crop faba beans decreased (P<0.05) from 25.3% at 82 days after
planting to 18.4 % at 166 days after planting in the 2002 production year, while during the 2003 production year
the CP content of whole crop faba beans decreased (P<0.05) from 28.2 to 19.5 % from 75 to 159 days after
planting. During 2002 the CF % of faba beans increased from 20.2 to 22.6%, while during 2003 CF % similarly
increased from 21.8 to 26.5%. The CF % for oats during 2003 increased from 25.6 to 36.9%. During the same
time the EE, Ca and P contents also decreased (P<0.05), while the NDF, CF and ADF contents increased (P<0.05).
Two milk production studies were conducted to compare the feed intake, milk yield and milk composition of
Holstein cows receiving either whole plant faba bean silage or oats as a hay or silage. Faba bean (Vicia faba)
silage (FBS) was compared to that of cows receiving either oat (Avena sativa) hay (OH) or oat silage (OS) and
in a 50:50 combination with FBS. Faba beans (cv. Ascot) and oats (cv. Sederberg) were planted on a
Glenrosa soil. Whole crop faba beans were ensiled 145 days after planting in an above ground concrete
bunker using a commercial bacterial inoculant after being wilted for one day.
In the first experiment, total mixed rations (TMR) containing FBS, OH or a 50:50 mixture of FBS and OH as
forage, together with a concentrate, were fed to three groups of seven lactating Holstein cows each. The
experiment was conducted according to a randomized block design. Cows were on average 112±44 days post
calving producing 24.0±6.2 kg milk/day. Milk production parameters of cows receiving diets containing different forages were compared by analysis of variance. The DM intake and milk yield of cows receiving
TMR’s containing FBS, OH or a mixture of 50:50 FBS and OH as forages did not differ (P>0.05), milk yields
being 18.9±1.9, 20.6±1.3 and 20.5±1.4 kg/cow/day respectively. With the exception of MUN, milk composition
parameters did not differ among treatments (P>0.10). Cows fed OH as roughage source had a higher
(P=0.06) MUN level in the milk. Results from this study indicate that FBS could effectively replace OH in
lactating dairy cow diets.
In the second experiment, total mixed rations (TMR) containing FBS, oat silage (OS) or a 50:50 mixture of FBS
and OS as forages, together with a concentrate, were fed to six Holstein cows according to a double 3 x 3 Latin
Square cross-over experimental design. Each cow received 13 kg DM either FBS, OS or a 50:50 mixture of
FBS and OS were fed as forages, together with three different concentrates at nine kg “as is” each, to each
cow. Cows were on average 108±30 days post calving producing 22.0±2.0 kg milk/day. DM intake, body
weight, milk yield and milk composition parameters of cows receiving diets containing different forages were
compared statistically. The DM intake and body weight of cows receiving TMR’s containing FBS, OH or a
mixture of 50:50 FBS and OS as forages did not differ (P>0.10), although body weight changes differed
significantly (P<0.10), i.e. 4.0±3.2, 8.8±3.2 and -6.0±3.2 kg respectively. The milk yield of cows receiving
TMR’s containing FBS, OS or a mixture of 50:50 FBS and OS as forages did not differ (P>0.10), milk yields
being 22.8±0.4, 21.4±0.4 and 21.9±0.4 kg/cow/day respectively. Of the milk composition parameters, the milk
CP(%) of cows fed TMR’s containing FBS differed (P<0.05) from the cows fed the 50:50 mixture of FBS and
OS, as well as cows fed the OS, being 2.82±0.02, 2.93±0.02 and 2.96±0.02% respectively. Results from this
study indicate that FBS could effectively replace OS in lactating dairy cow diets.
The South African database on in situ protein and fiber degradability values for whole crop faba beans and oats
is limited. The chemical composition of whole crop faba beans and oats constantly change as plants mature.
For optimal stage of ensiling and feed formulation it would be useful to have CP, NDF and ADF degradability
values available for whole crop faba beans and oats harvested at different growth stages. The objective of this
study was to determine the ruminal nutrient degradabilities of whole crop faba beans (Vicia faba) and oats
(Avena sativa). Whole crop faba beans and oats were cut at weekly intervals from 75 to 159 days after planting.
Effective DM, CP, NDF and ADF degradability values of faba beans and oats harvested at 117, 131, 145 and
159 days after planting were determined by using the in situ nylon bag technique. Three non-lactating Holstein
cows fitted with ruminal fistulae were used. Plant material put into Dacron bags was incubated in the rumen for
4, 8, 12, 24, 48, 72 and 96 hours. The degradability of DM, CP, NDF and ADF fractions of whole plant faba
beans and oats in four different growth stages (117, 131, 145 and 159 days from planting) did not differ (P<0.05)
among cows. The degradability of different fractions for both roughages were affected (P<0.05) by growth stage
and incubation hours. DM, CP, NDF and ADF disappearance of whole crop faba beans and oats at 117 and 159
days after planting differed (P<0.05) at 4, 8, 12, 24, 48, 72 and 96 hours of incubation time. The DM, CP, NDF
and ADF disappearance values were fitted to the non-linear model p = a + b (1- e-ct). The effective
degradabilities (P) could be calculated using a fractional outflow rate of k = 0.05. For whole crop faba beans,
parameter b (potentially degradable fraction) and parameter c (the rate at which b is degraded) all differed different forages were compared by analysis of variance. The DM intake and milk yield of cows receiving
TMR’s containing FBS, OH or a mixture of 50:50 FBS and OH as forages did not differ (P>0.05), milk yields
being 18.9±1.9, 20.6±1.3 and 20.5±1.4 kg/cow/day respectively. With the exception of MUN, milk composition
parameters did not differ among treatments (P>0.10). Cows fed OH as roughage source had a higher
(P=0.06) MUN level in the milk. Results from this study indicate that FBS could effectively replace OH in
lactating dairy cow diets.
In the second experiment, total mixed rations (TMR) containing FBS, oat silage (OS) or a 50:50 mixture of FBS
and OS as forages, together with a concentrate, were fed to six Holstein cows according to a double 3 x 3 Latin
Square cross-over experimental design. Each cow received 13 kg DM either FBS, OS or a 50:50 mixture of
FBS and OS were fed as forages, together with three different concentrates at nine kg “as is” each, to each
cow. Cows were on average 108±30 days post calving producing 22.0±2.0 kg milk/day. DM intake, body
weight, milk yield and milk composition parameters of cows receiving diets containing different forages were
compared statistically. The DM intake and body weight of cows receiving TMR’s containing FBS, OH or a
mixture of 50:50 FBS and OS as forages did not differ (P>0.10), although body weight changes differed
significantly (P<0.10), i.e. 4.0±3.2, 8.8±3.2 and -6.0±3.2 kg respectively. The milk yield of cows receiving
TMR’s containing FBS, OS or a mixture of 50:50 FBS and OS as forages did not differ (P>0.10), milk yields
being 22.8±0.4, 21.4±0.4 and 21.9±0.4 kg/cow/day respectively. Of the milk composition parameters, the milk
CP(%) of cows fed TMR’s containing FBS differed (P<0.05) from the cows fed the 50:50 mixture of FBS and
OS, as well as cows fed the OS, being 2.82±0.02, 2.93±0.02 and 2.96±0.02% respectively. Results from this
study indicate that FBS could effectively replace OS in lactating dairy cow diets.
The South African database on in situ protein and fiber degradability values for whole crop faba beans and oats
is limited. The chemical composition of whole crop faba beans and oats constantly change as plants mature.
For optimal stage of ensiling and feed formulation it would be useful to have CP, NDF and ADF degradability
values available for whole crop faba beans and oats harvested at different growth stages. The objective of this
study was to determine the ruminal nutrient degradabilities of whole crop faba beans (Vicia faba) and oats
(Avena sativa). Whole crop faba beans and oats were cut at weekly intervals from 75 to 159 days after planting.
Effective DM, CP, NDF and ADF degradability values of faba beans and oats harvested at 117, 131, 145 and
159 days after planting were determined by using the in situ nylon bag technique. Three non-lactating Holstein
cows fitted with ruminal fistulae were used. Plant material put into Dacron bags was incubated in the rumen for
4, 8, 12, 24, 48, 72 and 96 hours. The degradability of DM, CP, NDF and ADF fractions of whole plant faba
beans and oats in four different growth stages (117, 131, 145 and 159 days from planting) did not differ (P<0.05)
among cows. The degradability of different fractions for both roughages were affected (P<0.05) by growth stage
and incubation hours. DM, CP, NDF and ADF disappearance of whole crop faba beans and oats at 117 and 159
days after planting differed (P<0.05) at 4, 8, 12, 24, 48, 72 and 96 hours of incubation time. The DM, CP, NDF
and ADF disappearance values were fitted to the non-linear model p = a + b (1- e-ct). The effective
degradabilities (P) could be calculated using a fractional outflow rate of k = 0.05. For whole crop faba beans,
parameter b (potentially degradable fraction) and parameter c (the rate at which b is degraded) all differed
v
significantly (P<0.05) between four different growth stages (117, 131, 145 and 159 days from planting) of plant
maturity for CP, NDF and ADF. In oats, parameter b and parameter c did not differ (P>0.05) between the four
different growth stages (117, 131, 145 and 159 days from planting) of plant maturity.
Results from this study could make a valuable contribution towards the South African databases on faba bean
and oats nutrient values and can be used in dynamic feed formulation. Faba beans cut as fresh crop or silage
may in the foreseeable future play an increasingly larger role in the feeding of dairy cattle in the Winter Rainfall
Region of South Africa. As in the case of lupin silage, though with much higher protein content, farmers will be
able to produce their own quality and high protein roughage. The nutritive properties of faba bean silage holds
great promise as a forage in lactating dairy cows.